Tissue to Air Ratio
||This article may be too technical for most readers to understand. (June 2008)|
The TAR at a point in a water phantom irradiated by a photon beam is taken to be the ratio of the total absorbed dose at that point to the absorbed dose at the same point in a minimal-scatter phantom with just-sufficient build-up.
Tissue-air ratio is defined as the ratio of the dose to water at a given depth to the dose in air measured with a buildup cap. Measurements for each are taken using an ion chamber for identical source to detector distances and field sizes.
See also 
- Johns H. E. and Cunningham J. R. (1983). The Physics of Radiology. Charles C. Thomas Publ.
- Hendee W., Ibbott G. and Hendee E. (2005). Radiation Therapy Physics. Wiley-Liss Publ. ISBN 0-471-39493-9.
- Faiz M. Khan. (2010) "The Physics of Radiation Therapy " Lippencott, Wilkins and Williams Publ.